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<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
	字符串:123“abc”456
	匹配结果:abc

	<script type="text/javascript">
	var str = '123"abc"456';
	var reg = /(?=\d)\w{3}/g;
	alert( str.match(reg) );
	</script>
</body>
</html>